Flood Mitigation – We Need Miles and Miles of New Hedgerows

To suggest any species for planting (be it for amenity and landscaping purposes, agriculture or forestry) with the swing between drought conditions to flooding that we now have to accept as normal, indeed prepare ourselves for worse, is simply stupid unless we sort out the soil first. And both in the UK and France as well as most of the rest of the world the majority of our soils are in poor shape as a direct result of poor management by humans.

There are widespread comments that rain is falling on ‘saturated’ ground and thus the flooding is exasperated – but with the vast majority of land this is simply not true. The soil is saturated as far down as the first impermeable layer, which in the majority of urban, peri urban and rural landscapes is not that deep – certainly nowhere near as deep as the groundwater level, which despite the rains is nowhere near as high as it has been throughout much of modern history.

40cm on average – dig down 40cm and you will likely discover a soil pan. It may have been created  by the countless passings of a plough, a rotovator, or other machinery or possibly the limit of a spade.

New tree plantings often suffer as a result of this pan. If the trees have survived their dose of disease courtesy of an unknown nursery, their planting too deep or too shallow in an unprepared field, they will go on to develop a shallow lateral root system which does little to protect or enhance the ‘new woodland’ habitat that they are reported to be.

Commercial forestry ground preparation is much more advanced than NGOesque ‘new woodlands’ – it may look ugly in comparison, but well designed ground preparation by mixed dolloping, ploughing, 3degree drainage etc., is highly effective in slowing and trapping substantial amounts of water. In upland areas with high soil carbon where much of this forestry has taken place in the 20th century in the UK, the ground preparation has resulted in substantial filtering systems, which have the potential of reducing surface water run off considerably. Many unprepared new woodland sites cannot claim such additional benefit.

Tree planting for landscaping purposes often involve substantial ground preparation also, which if carried out correctly can help mitigate urban surface water run off considerably. Good design can easily incorporate good landscaping to achieve real sustainable development that can progress our adaptation to climate change, our resilience and soil is the hub to work from.

When reviewing tree planting as has been done recently, and not before time, we must not throw the baby out with the bath water and dismiss it entirely. It can work, it has worked, to provide a host of benefits that include mitigation against flooding risk but we have to take the planting process much much more seriously as well as grapping the opportunity to reinstall those quintessential elements of a British landscape proven to reduce flooding and allow for a two way water flow (downwards in times of heavy rainfall and upwards in dry periods): Dry Stone Walls, Earth Bank Hedgerows, Retaining Walls, Swales, Ditches (a good ditch is a work of art as well as  one of the most simple yet effective engineering ever) and even Covered Leats.

wibbly wobbly ha ha2

And one habitat should become sacrosanct: The Riparian Zone. Despite condemnation from many quarters, flood plains in Britain remain a favourite zone for developers, who have proven time and time again to be useless at installing the engineering really required and leaving the costs up to the insurance industry as well as utter long term misery for householders. Paying to allow the natural regeneration of Britains riparian zones will surely provide future dividends beyond our wildest dreams.

And get planting new hedgerows, miles and miles of new hedgerows and fatten existing hedgerows. There is no need for agroforestry in the UK – hedgerows are far better; providing slow effective drainage, acting as biodiversity corridors also as well as extending a national and / or regional identity to the British landscape to adorn the biscuit tins of future generations.



Filed under Trees and Woodlands

2 responses to “Flood Mitigation – We Need Miles and Miles of New Hedgerows

  1. Gary Grant

    I agree – we need more and better hedgerows, however I wouldn’t rule our agroforestry in the UK – various possibilities should be considered

  2. I know you are right and agroforestry should be a much more prominent consideration. Using the basis of a hedgerow, in particular the foundations, it has much more mileage in terms of contemporary landscape design – in the urban environment also(?). Thanks for the comment and flattered also that you have.

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